Detecting Chrome OS with Javascript

I want to detect Chrome OS with Javascript, and I'm using navigator.userAgent for this. Now, I'm running Chrome OS, and my navigator userAgent is

Mozilla/5.0 (X11; CrOS armv7l 6680.78.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.102 Safari/537.36

Now. I used Regular Expressions to check for the style of the userAgent, and wrote the code below.

<script>
    if ( navigator.userAgent = /^Mozilla\/\d{1}^.\d{1}^(X11; CrOS i\d{3} \d{1}^.\d{2}\d{3} ^AppleWebKit\/\d{3}^.\d{2} ^(KHTML, like Gecko) Chrome\/ \d{2}^.\d{1}^.\d{3}^.\d{2} ^Safari\/\d{3}^\d{2}/ ){
      console.log(navigator.userAgent);
    } else {
      console.log(navigator.userAgent);
    }
</script>

Now, upon loading this Script, I get an error.

Uncaught SyntaxError: Invalid regular expression: /^Mozilla\/\d{1}^.\d{1}^(X11; CrOS i\d{3} \d{1}^.\d{2}\d{3} ^AppleWebKit\/\d{3}^.\d{2} ^(KHTML, like Gecko) Chrome\/ \d{2}^.\d{1}^.\d{3}^.\d{2} ^Safari\/\d{3}^\d{2}/: Unterminated group

What is wrong here with my code?

Solution

What it's complaining about is that you have an ( with no matching ). In a regular expression, ( and ) define capture groups and have to be balanced. If you want to match an actual ( or ), you have to escape it with a backslash.

But there are several other issues. It doesn't make sense to have ^ ("beginning of input") anywhere but the beginning of the expression, for instance.

But I don't think anything else puts CrOS in the user agent, so perhaps simply:

if (/\bCrOS\b/.test(navigator.userAgent)) {
    // yes, it is (probably, if no one's mucked about with their user agent string)
} else {
    // No, it isn't (probably, if no one's mucked about with their user agent string)
}

The \b are "word boundaries" so we don't match that string in the middle of a word. Note that I left it case-sensitive.

Side note: I find https://regex101.com/#javascript (which I am not in any way affiliated with) quite useful for debugging regular expressions.

Side note #2: The above is useful if you really do need to detect ChromeOS, but if it's just a feature you need to check for, as jfriend00 points out, feature detection may be the better way to go.